An archaeologist searches for both treasures and trash -- the signs of our earlies­t ancestors, a lost civilization or our recent past. After intensive study, extensive mapping and a painstaking dig, an archaeologist discovers a find. It might be a fragment of bone, a shard of clay or an ancient coin. As the dust and dirt settle through the archaeologist's screen, an irregular clump of clay appears. The clump doesn't crumble under light pressure. The archaeologist knows it's actually a potsherd, clay pottery tough enough to withstand the stresses of millennia.

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­Years of studying taxonomy might help the archaeologist roughly date the fractured fragment on-site -- elim­inating the possibility that it's actually just a grungy plate from the recent past. Other consultants are soon brought in -- geologists, biologists or art historians -- people who help create an accurate, complete context for the little shard of clay. Piece by piece, history emerges from the earth.

Archaeology is the study of humanity's material remains: its buildings, art, everyday objects, trash and even bodies. Archaeologists are scholars who study every facet of their scholarly realm. They're explorers who map out and chart excavation sites. They're scientists who document and verify their finds. And they're historians who flesh out the past.

Because archaeology is such a massive field, it's usually broken into periods, like Prehistoric or Industrial archaeology, or into geographical areas, like Classical or Mesopotamian archaeology. Sometimes archaeology's subfields are practically independent disciplines. For instance, forensic archaeologists work with law enforcement officers to locate evidence or study potential gravesites. Underwater archeologists study shipwrecks or other watery remains of human industry and must be proficient divers. Archaeologists are sometimes confused with paleontologists, scientists who study the remains of prehistoric plants and animals, but not humans or our hominid ancestors.

In this article, we'll learn how the study of archaeology developed, how an archaeologist works and look into some of archaeology's biggest finds along the way. ­­

The History of Archaeology

Ancient Ruins like those of the Temple of Hadrian on the Aegean Coast of Turkey attracted the attention of the Renaissance elite.

Today archaeology is a precise science. Archaeologists' tools include radioactive carbon dating and geophysical prospecting. The discipline is strongly influenced and even driven by humanities like history and art history. However, it is, at heart, intensely methodical and technical. But archaeology hasn't always been precise. In fact, it hasn't always been a science.

Archaeology originated in 15th and 16th century Europe with the popularity of collecting and Humanism, a type of rational philosophy that held art in high esteem. The inquisitive elite of the Renaissance collected antiquities from ancient Greece and Rome, considering them pieces of art more than historical artifacts.

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The desire for antiquities and an interest in the ancients soon led to sponsored excavations and the development of Classical archaeology. Herculaneum and Pompeii, the two famous cities destroyed and preserved by the A.D. 79 eruption of Mount Vesuvius, were excavated in part because the Queen of Naples longed for ancient statuary.

Napoleon Bonaparte's 1798 invasion of Egyptushered in a new era in archaeology. In order to understand the Egyptian people and their past, Napoleon brought with him a think tank of 175 scholars: the Institute of Egypt, or the Scientific and Artistic Commission. The troop came with its own traveling library, scientific tools and measuring instruments. By 1809, the scholars and scientists published the illustrated "Description of Egypt," a book that helped launch a mania for all things Egyptian. By 1822, Jean-François Champollion had deciphered the Rosetta Stone, unveiling the secrets of ancient Egypt's hieroglyphics to the world.

Scientific archaeology continued to develop in the 19th century with advances in the studies of geology and biology. Charles Lyell helped spread the modern geologic system of uniformitarian stratigraphy, which gave archaeologists a reliable timescale on which to date items. The work of Lyell and the publication of Charles Darwin's "The Origin of Species" soon popularized the idea of evolution. Belief in man's antiquity exploded the study of prehistoric archaeology.

The 20th century opened with radical developments in the field: the 1904 publication of Flinders Petrie's "Methods and Aims in Archaeology" developed a systematic method for excavation. Massive finds like the 1922 discovery of King Tutankhamen's tomb or the 1926 unearthing of the Royal Tombs at Ur -- which brought the entire forgotten Sumerian civilization to life -- helped glamorize archeology. Archaeologists began to work beyond the Near East, Mediterranean and Europe, and the subject finally became an academic discipline.

In the next section, we'll dig deep and learn about an archeologist's work.

Quiz Corner

Crystal skulls are among the most mysterious of archaeological oddities. Test your knowledge in the Crystal Skull Quiz.

An Archaeologist's Work: Fieldwork and Excavation

It's easy to imagine the archaeologist in the field -- a modern-day adventurer discovering the mysteries of the past before whisking off to a new, even more fascinating site. The archaeological process, however, begins long before the spade hits the dirt. Every excavation involves years of study, scouting and planning.

Some archaeologists consider fieldwork the entire outdoor archaeological process, from scouting to digging. Others consider fieldwork the pre-dig activity and differentiate it from actual excavation. This preliminary work includes everything from consulting aerial photographs, old maps and physical references in literature, or even using high-tech methods like geophysical prospecting, a technique that measures electrical conductivity in soil.

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This type of meticulous fieldwork prepares archaeologists for planned excavations. However, not all excavations are planned; there are also accidental excavations and rescue excavations. Some of the greatest archaeological finds are simply fortunate discoveries. In 1940, four French schoolboys found themselves in a chamber ornamented in Upper Paleolithic masterpieces. They had simply been exploring a tunnel exposed by an uprooted tree. In 1947, a Bedouin shepherd discovered the first Dead Sea Scrolls, the earliest copies of any Biblical books, while searching for a stray animal.

Sometimes, accidental finds become rescue excavations. Construction projects often unearth archeological sites that must be explored and recorded quickly so that business can continue. When a city has as many layers of history as Rome, archeological finds are inevitable; every request for a building permit -- all 13,000 annually -- requires an archaeological evaluation [source: National Geographic]. Sometimes such thoroughness can cripple a city. Rome struggles to meet the demands of its 2.8 million citizens while preserving its history [source: U.S. Department of State].

But because excavation inherently destroys a site, an archaeologist must record the placement of every artifact. This record ultimately becomes a primary source for other archeologists and historians to consult since the actual primary source -- the site itself -- no longer exists in its original form. The archaeologist also brings in experts from other disciplines like geology or metallurgy to help analyze the finds.

In the next section, we'll learn about archeology's dark side: smugglers, robbers and bungling amateurs.

Save the Date

For an artifact to have meaning and relevance, an archeologist must be able to assign it a date. Archaeologists have used a variety of techniques to make sense of the past:

Self-dating: An item like a coin already comes with a date -- no questions asked.

Relative dating: The date of an unknown item can be interpreted by the known dates of surrounding items.

Clay-varve counting: Man's written chronology only goes back 5,000 years but by counting layers of varves, laminated sediments that accumulate annually, geologists and archaeologists can extend this chronology significantly.

Dendrochronology: By counting the growth rings of trees, archeologists can compile a chronology or historical record and precisely date wood.

Potassium-argon dating: Archaeologists can establish the date of minerals and rocks by comparing rates of radioactive argon to radioactive potassium. Potassium-argon dating can set a chronology that dates back at least 2,000,000 years. This type of dating helped determine the age of the earliest man's remains.

Thermoluminescence: By measuring the intensity of light energy, archaeologists can determine how long a substance was exposed to radiation

Amateur Archaeology and Robbers

Peru, which is wealthy in archeological artifacts and historic sites like Machu Picchu, struggles to protect its treasures.

Through research and interpretation, archaeologists transform material remains with unknown meaning into items of historical significance. They piece together lost civilizations, solve ancient medical mysteries and find out how we got to where we are today. But their work hinges on accuracy -- a disrupted site is less likely to hold verifiable clues. And while non-archaeologists sometimes make important accidental discoveries, amateur archaeologists and looters often destroy, displace or steal what has been miraculously preserved for years.

To prevent or at least curtail such destruction, many countries have antiquities laws. In the United States, the Antiquities Act prohibits the excavation or destruction of any archaeological materials on government land. The act has been in place since 1906 -- right around the time archaeology became a recognized academic subject.

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However, actually protecting sites is a difficult matter. The locations of highly sensitive archeological areas are sometimes kept secret. Others are already too well known by looters and casual explorers to stay hidden. State archaeological agencies might mark such sites with "Don't Dig" signs but clear warnings often tantalize potential thieves, alerting them to the possibility of buried treasure. The New York Archeological Council even posts less- alluring signs like "Environmentally Sensitive Zone: Do Not Enter" to deter would-be looters or curious hunters.

Macedonian police recovered these Bronze Age sculptures from artifact smugglers. Authorities believe Macedonia has lost more than a million archaeological artifacts to Europe's black markets since 1991.

Some countries struggle to defend their artifacts from international smugglers. The Peruvian government estimates at least $18 million worth of artifacts and goods are stolen and smuggled annually [source: Economist]. In an attempt to keep tabs on excavations, Peru's National Institute of Culture (INC) registers historic sites and requires that local artifact collections are also registered. They've even partnered with the International Council of Museums -- a group with links to UNESCO -- to create a list of commonly smuggled items in the hope that art dealers and customs officers will be able to recognize illegal goods.

But for people who want to excavate without stealing artifacts or breaking federal laws, amateur archaeology programs offer the chance to work at real active sites. The popular Dig for a Day program in Israel charges volunteers for access to the National Park of Beit Guvrin, King Herod's ancestral home. Guests dig and sift for pottery shards and explore an unexcavated cave system.

To learn more about archaeology, look over the links on the next page.